When detecting an internal defective state at a bend of a laminated part made of composite materials such as fiber-reinforced plastics (FRP), an ultrasonic transducer that transmits and receives ultrasonic waves is usually used.
The ultrasonic transducer has a transducer main body that has, on a front end side thereof, an oscillating plane having a bent shape in a side view and corresponding to a larger or smaller diameter curved surface formed at the bend of the laminated part. The oscillating plane of the transducer main body has a plurality of oscillators arranged in a bent direction of the oscillating plane of the transducer main body. Each oscillator transmits an ultrasonic wave toward the bend of the laminated part and receives a reflected wave from the bend of the laminated part. The oscillators are electrically connected to a controlling unit.
When detecting an internal defective state at the bend of the laminated part, the ultrasonic transducer is moved relative to the laminated part so that the oscillating plane of the transducer main body faces the larger or smaller diameter curved surface formed at the bend of the laminated part. The plurality of oscillators transmit ultrasonic waves toward the bend of the laminated part and receive reflected waves from the bend of the laminated part. According to received signals from the plurality of oscillators (flaw detecting signals from the ultrasonic transducer), the controlling unit nondestructively detects an internal defective state at the bend of the laminated part.
Related arts concerning the present invention are disclosed in, for example, Japanese Unexamined Patent Application Publications No. 2003-90829 and No. H06-18488.